Internal-combustion engine operating on the two-stroke cycle



March 10, 1931; I p. FQTH 1,796,094

INTERNAL COMBUSTION ENGINE OPERATING ON THE TWO-STROKE CYCLE Filed Jan.29. 1929 NVENTU R- m 5- c/UL Patented d Mar. 10, 1931 siren sraras ATENrFFHCE PETER FOT'H, or ROWNE, ronayn, ASSIGNORTO THE FIRM sULzERrREREsSOCIETE ANONYME, or WINTERTHUB, SWITZERLAND INTERNAL-COMBUSTION ENGINEOPERATING ON THE TWO-STROKE CYCLE Application filed January 29,1929,.Serial No. 335,920, and in Switzerland February 10, 1928.

This invention relates to internal combustion engines operating on thetwo-stroke cycle of the kind in which a scavenging charge is admittedand exhaust gases escape respectively through ports situated in thecylinder wall.

In known engines of this type either the scavenging charge is admittedalways in the same direction and the exhaust gases are dischargedthroughan exhaust port situated on the same or the opposite side of thecylinder to the scavenging ports, or the scavenging charge is directed,during the initial part of the scavenging period, towards the centre ofthe cylinder owing to the shape or construction of the port or ports andsubsequently towards the end of the scavenging period, is

deflected more along the cylinder wall. In

the first of the above prior arrangements not only are rotating cores ofexhaust gases apt to be formed in the centre portion of the .cylinderbut further the corners of the cylinder are not eificiently scavenged,while in the second prior arrangement the contents of the cylinder areso swept through by the scavenging charge that the desired purity ofcharge is not attained even with considerable consumption of scaven ,fngair.

According to the present invention the air inlet ports are subdividedand the charge entering therethrough is caused during the initial partof the scavenging period to flow along the cylinder wall towards thecylinder head and subsequently is gradually deflected obliquely towardsthe cylinder axis so as to expel the exhaust gases through one or moreexhaust ports disposed opposite to the scavenging port.

The means employed to eflect the desired change in direction of thescavenging charge may vary. Thus the flow through the subdivision orsubdivisions of the air inlet ports which are uncovered by the pistonduring the initial part of the scavenging period may be caused to takeplace in a di erent direction from that through the subdivision orsubdivisions uncovered during the later part of the scavenging period.Alternatively, the desired change indirection of flow of the scavengingcharge may be effected by a secondary scavenging charge admitted intothe cylinder so as to strike the main scavenging charge and deflect itin the desired manner, the manner in which the main and secondaryscavenging charges are admitted being such that the eflect of thesecondary scavenging charge on the direction of flow of the mainscavenging charge varies throughout the scavenging period so as toproduce the desired variation in the direction of ,flow of the mainscavenging charge. In such an arrangement the rate of flow of thesecondary scavenging charge at its admission into the cylinder isconveniently greater than that of the main scavenging charge.

In any case the upper edge of the main scavenging port or portspreferablylies above the upper edge of the secondary scavenging andexhaust ports so as to avoid undue throttling of the charge entering thecylinder dur- F ing the later part of the scavenging period.

Further where a secondary scavenging charge is employed, this isconveniently admitted in such a manner as to prevent as far as possiblea premature escape of the scavenging charge from the engine cylinderthrough the exhaust port or ports.

The invention may be carried into practice in various ways but variousconstructrons according to this invention are illustrateddiagrammatically by way of example in the accompanying drawings, inwhich Figure" 1 shows diagrammatically the manner in which scavengingair flows into the cylinder in known prior arrangements,

Figure 2 shows diagrammatically the manner in which scavenging iseffected accord ing to the present invention,

Figures 3 and 4 show one construction in which scavenging is effected in-the manner according to the present invention,

Figure 5'shows one alternative construc tion according to thisinvention, and

Figures 6, 7 and 8 show another alternative construction according tothis invention. In the previously known arrangement as illustrated inFigure 1 in which the scavenging air was admitted into the cylinder 7through non-subdivided scavenging ports 6, and the flow of thescavenging air took placeduring and to effect adversely the combustionon the.

. For example,

the scavenging period successively in the directions indicated by thearrows 5, 4, 3, 2, 1, in Figure 2, this air impinged first a ainst theopposite cylinder wall and was de ected thereby upwards whereby rotatingcores of burntgases as indicated at a and I) in Figure 1 were apt to beformed. in the cylinder next power stroke.

In an engine according to the present invention', however, flow throughthe. main scavenging port 6 takes place successively in the directlonsindicated by the arrows 1, 2,

3, 4, in Figure 2. That is to say, during the initial scavenging period,say when the crank is in position '1 indicated in Figure 2, thescavenging air flows in the direction indcated by the arrow 1 and as thecrank advances successively through the positions 2, 3, 4 and 5 so thedirection of flow of the scavenging air is also deflected sov as tofollow successively the direction 4 and 5. Thus the exhaust gases areexpelled through the exhaust port 8 under the action of the scavengingair current as it swings downwards. V

In Figure 2 the scavenging port 6 is not shown as subdivided as it wouldbe in practice since thepurpose of this figure is merely to indicatediagrammatically the manner in which scavenging is effected according tothis invention.

The change in direction of flow of the main scavenging air currentduring the scavenging period may be eflected in various ways. as shownin'Figures 3 and 4, the partitions subdividing the scavenging port 6 maybe in the form of movable guide vanes 11 pivoted about horizontal axes 9and adapted to be rocked during the scavenging period by a. control rod10 pivoted thereto. Figure 3 indicates the condition during the initialpart of the scavenging period in which the scavenging air current. isdirected along the cylinder wall towards the cylinder head in thedirection indicated by the arrow 1. As the scavenging period progressesso the guide vanes 11 are rocked by the rod 10 so that during the laterpart of a scavenging period as the piston 12 moves upward as indicatedin Figure 4, the scavenging air current is deflected towards the centreof the cylinder in the direction of the arrow 5.

In order to avoid undue throttling of the scavenging air towards the endof the scavenging period, the subdivided scavenging ports 6 convenientlyextend upwards above the level of the upper edge of the exhaust ports 8as shown. I

In the alternative arrangement indicated in Figure 5, the change ofdirection of flow of the main scavenging air current is effected bymeans of a secondary or auxiliary scavenging air current admittedthrough a of the arrows 2, 3,

wards the centre of pass through the valve 22.

the exhaust ports 8, the main, scavenging charge enters through the mainscavenging ports 6, for instance in the direction of the arrow 15, thismam scavenging charge will be deflected along the adjacent cylinder'wallby the secondary scavenging air current entering in the directionof thearrow 16 so that there will be produced a scavenging air ourrentdue tothe two currents in the direction of the arrow 17 Owing to the increasein the cross-sectional area of the secondary scavenging ports 14 due tothe downward movement of the piston 12, the effect of the secondaryscavenging air current on the direction of flow of the main scavengingair cur-, rent will be reduced as the piston descends and the mainscavenging air current Will become deflected as the scavenging periodprogresses as indicated by thearrow 18 tothe cylinder in the manneraccording to this invention;

A still further arrangement for carrying out the present invention isshown in Figures 6, 7 and 8. This arrangement is somewhat similar tothat shown in Figure 5 except that the upper and lower divisions 20,

with separate chambers having a valve 22 dividing them.

Figure 6 shows the condition during the initial part of a scavengingperiod during which after equalization of pressure has taken place themain scavenging air will flow through the lower scavenging ports 21,which may be shaped so as to direct the air more towards the cylinderhead, and will be deflected at first along the cylinder wall by thesecondary scavenging air current entcr ing at higher speed through theports 14 so that there will take place during the initial part of thescavenging period scavenging of the outer parts of the cylinder. The airen'- tering through the upper main scavenging ports 20 will not, at thisstage, have any considerable efl'ect on the direction of flow of thescavenging current, since the rate of flow through the ports 20 isreduced owing to the air flowing to this port having to open and As thescavenging period progresses the secondary scavenging ports 14 will beopened further and the rate of flow of air therethrough will decrease sothat the action of the secondary scavenging air current on the mainscavenging air current will be reduced and the mam scavenging aircurrent will thus enter the cylinder obliquely as shown in Figure 7.Towards the end of the scavenging period the direction of flow of themain scavenging air current will be substantially that of the flowthrough the upper ports 20 as indicated in Figure 8, since at this stageair can flow with undiminished velocity through these ports, the valve22 being now open. Thus during the later portions of the scavengingperiod, the main scavenging air current is directed towards the centreof the cylinder to expel any traces of waste gases which may stillremain. v

With either of the arrangements illustrated in Figure 5 or in Figures 6,7 and 8, a further improvement as regards the consumption of scavengingair may be obtained by admitting the secondary scavenging air currentinto the cylinder in such a manner as to avoid as far as possible apremature es cape of air from the engine cylinder into the exhaust.

In order to show more clearly the manner in which the direction of flowof the main scavenging air current varies according to this invention,the subdivided main air scavenging port as well as the exhaust ports areindicated in the drawings merely diagrammatically. In practice it isadvisable to arrange the air inlet ports 20 and 21 on one side of thecylinder and the exhaust ports 8 on the opposite side of the cylinder,and to arrange the secondary scavenging'air ports 14 beneath the latterso as to extend throughout their length considered circumferentially ofthe cylinder. Further, if desired, the secondary scavenging air portsmay be constructed so that the air current is admitted into the c linderin a direction approximately at rlght angles to the axis of the pistoninstead of inclined thereto as shown.

Again, the exhaust port may be controlled by separate valves instead ofby the piston while the desired effect may be obtained in other waysthan by admitting the scavenging air in diflerent directions through thevarious subdivisions of the main scavenging port, by employing secondaryscavenging currents or by providing movable guide vanes in the mainscavenging ports without departing from this invention. r

I claim:

1. In a two-stroke internal combustion engine, a cylinder having a setof principal, sub-divided, scavenging ports on one side of the cylinder,and a set of secondary scavenging ports arranged on the opposite sidethereof, the relation between the arrangement of said ports being suchthat a stream of air introduced through said principal ports during thescavenging period will be deflected 'by an impinging stream of airintroduced through said secondary ports and directed first axially ofthe cylinder and subsequently at a gradually increasing angle to thecylinder axis.

2. Apparatus according to claim 1, further 3. Apparatus according toclaim 1, including means for closing the principal subdivided scavengingports later 'than the other in order to avoid throttling.

4. A method of scavenging the cylinder of a. two-stroke internalcombustion engine,

comprising applying a principal scavenging force in a certain directionwithin the cylinder, and applying against this force a secondary force,said secondary force being directed against 'said principal force insuch a direction as to deflect the resultant first towards the end ofthe cylinder and thereafter obliquely towards the cylinder axis.

5. A method of scavenging the cylinder of a two-stroke internalcombustion engine, comprising applying a principal scavenging force in acertain direction within the cylinder, and applying against this force asecondary force in a direction substantially at right angles thereto.

6. A method according to claim 4, further characterized by the fact thatthe secondary force is applied with an initial value greater than thatof the principal force.

7 A method according to claim 4, in which the secondary force is socombined with the other force in the cylinder as to prevent prematureexhaust from the cylinder.

In testimony whereof I have afiixed my signature.

PETER FQ'IH.

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